The present invention relates to a linear guide apparatus, more particularly, to a linear guide apparatus of a type that is lubricated with a lubricant-containing polymer in such a way that a plurality of rolling elements rolling within a slider are automatically supplied with the lubricant from a seal device over an extended time.
A conventional linear guide apparatus in common use is typically shown in FIG. 6 and includes an axially extending guide rail 1 having rolling grooves 3 in outer surfaces and a slider 2 mounted over the guide rail 1. The slider 2 includes a slider body 2A and an end cap 2B fitted at both ends of the slider body 2A. The slider body 2A has two wings 4, each of which has rolling grooves (not shown) in its inner lateral surface that are confronted with the rolling grooves 3 in the guide rail 1. The slider body 2A also has return paths (not shown) that are formed axially through the thick-walled portion of each wing 4 and along which the rolling elements are to be returned. End caps 2B have curved paths (not shown) that allow the rolling grooves 3 in the slider body 2A to communicate with the return paths which are parallel to the grooves 3, thereby forming circuits for the circulation of the rolling elements. The rolling elements which are typically in the form of steel balls are loaded in the circuits.
The slider 2 mounted over the guide rail 1 moves smoothly along the rail via the rolling elements rolling in both the opposed grooves. While the slider 2 moves, the rolling elements circulate endlessly along the circulation circuits in the slider 2.
The slider 2 is fitted with a dustproof seal device that closes the openings of the clearance from the guide rail 1 and which, as shown in FIG. 7, includes side seals 5 provided at both ends (or at the end face of each end cap 2B) and under seals 6 provided on the underside. Conventionally, these seals are made of rubbers such as NBR (acrylonitrile butadiene rubber).
In order to lubricate the above-described linear guide apparatus, a grease nipple 7 is fitted on the slider 2 and grease or some other lubricant is supplied through this nipple into the circuits for the circulation of the rolling elements, thereby lubricating the elements as they roll within the slider.
This linear guide apparatus lubricated directly with the grease or lubricant has involved a problem in that when it is used in a hot environment, the grease or lubricant packed in the slider becomes fluid and flows out of the slider; because of this early depletion of the lubricant, refilling work is necessary at short intervals. Another problem is associated with use in an environment containing much foreign matter as exemplified by wood waste, metal shavings and other powdery foreign objects; in this situation, the packed lubricant is deprived of the oil content by absorption into the foreign matter and there is high likelihood for the occurrence of poor lubrication.
With a view to solving these problems, a seal device including lubricant-containing polymer members has been proposed in Unexamined Japanese Patent Publication No. Hei. 6-346919. In the proposed device, the seal members such as side seals and under seals to be fitted on the slider are formed of a lubricant-containing rubber or synthetic resin such that the lubricant would seep out of the seal members continuously over an extended time to be supplied automatically to the circuits in the slider for the circulation of the rolling elements.
However, the linear guide apparatus equipped with this seal device including conventional lubricant-containing polymer members has involved the following problems.
(1) The seal members in the form of the lubricant-containing polymer member contains such a great amount of lubricant that it is considerably low in mechanical properties such as hardness and strength compared to seal members made of more conventional materials such as NBR and, therefore, if they are used as such, they are prone to break, crack or otherwise fail to perform the sealing function.
(2) Conventional side seals in common use include a rubber (e.g. NBR) member and a metallic reinforcement plate (core metal), which are bonded together with an adhesive to make an integral body. However, this approach is not equally applicable to the case of joining the lubricant-containing polymer member and the core metal since the high oil content of the polymer member not only presents difficulty in the bonding operation but also increases a possibility of separation between the two members.
(3) In order to fit protectors or reinforcing side seals on outer surfaces of the seal device, they have to be secured by threading screws into the lubricant-containing polymer member through mounting holes. However, the tightening of the screws can potentially deform, crack or otherwise damage the lubricant-containing polymer member which, as already mentioned, is low in physical properties such as hardness and strength.
As another problem, local pressure is exerted on the tightened areas, from which the lubricant seeps out to cause its early depletion.